Electric discharge device



Nov. 29, 1949 H. L. THoRsoN 2,489,873

ELECTRIC DISCHARGE DEVICE Filed Sept. 2l, 1946 H awry L Th Orson,

His Attorney.

Patented Nov. 29,1949

ELECTRIC DISCHARGE DEVICE Harry L. Thorson, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application September 21, 1946, Serial No. 698,495

1 Claim.

My invention relates to electric discharge devices and more particularly to improved highfrequency, high-power discharge devices.

In copending Elder and Crawford application, Serial No. 650,701, led February 27, 1946, now United States Patent No. 2,489,872 issued November 29, 1949, and assigned to the assignee of the present invention is described and claimed an electric discharge device which is particularly adapted for high power applications at moderately high frequencies. The present invention is in the nature of an improvement on the invention disclosed and claimed in the Elder et al. application and relates particularly to an improved seal and envelope structure which facilitates installation and removal of the discharge device. The present invention also contemplates a discharge device employing a screen grid which together with the control grid are mounted in a novel manner from an improved envelope construction.

It is an object of my invention to provide a new and improved electric discharge device.

It is another object of my invention to provide a new and improved high power electric discharge device for operation at high frequencies.

It is a still further object of my invention to provide a new and improved electric discharge device which is easily installed and removed from the co-operating circuit elements.

Further objects and advantages of my invention will become apparent as the following description proceeds, reference being had to the accompanying drawing, and its scope will be pointed out in the appended claim. In the drawing, the single gure is an elevational view, in section, of a transmitting type electric discharge device embodying my invention.

Referring now to the drawing, the illustrated embodiment of my invention comprises an envelope including an anode I, in theform of a copper tube closed at one end and outwardly flared at the opposite end. The ared end is joined to a conical sealing member 2 which may to advantage be formed of one of the iron-nickelcobalt alloys. The member 2 is sealed at its upper end to the lower edge of a cylindrical insulator 3 which is preferably of glass having an expansion characteristic matching that of the sealing member 2. A second cylindrical insulator 4, having a diameter somewhat less than that of the first insulator', is sealed thereto by a cylindrical sealing member 5 which has a generally stepwise configuration in a transverse plane. As will become apparent at'ga later point in-the specification, the member 5 provides a ring termin-al for the screen grid of the device. In a similar manner, a still smaller hollow cylindrical insulator 6 is sealed to the insulator 4 by a cylindrical member 'I having a stepwise transverse section and which provides a terminal for the control grid of the device. The cathode terminal, which also serves as a terminal for one side of the heater current supply voltage, is provided by a portion of the envelope provided by an annular metal member 8 which, as clearly shown in the drawing, has a substantially inverted U-shaped section in a transverse plane. The member 8 has one arm of the U-shaped section sealed to the upper end of the cylindrical insulator B and the inner arm sealed to the upper end of a smaller glass insulating ring 9. The inner arm of the member 8 and the insulating ring 9 dene a reentrant portion of the envelope which is closed at its lower end by a cup-shaped metal member I0 sealed to the lower end of the ring 9. A second terminal for supplying heating current to the filament of the device is provided by a conducting stud I I which is brazed, or otherwise bonded, to the bottom of the cup-shaped member I0. As will be apparent from the drawing, the insulating ring 9 insulates the terminals 8 and l I which provide the heating current supply terminals.

A source of electrons is provided in the device by a cage-type cathode including a plurality of rod-like elements I2 which are supported concentrically within the tubular anode I and which are joined at one end to -a cup-like metal member I3. The member I3 is apertured centrally to receive an insulator I4 which transmits force to the lower end of the lamentary members l2, and lwhich is engaged by a force-transmitting tubular member I5. The member I5 is biased downwardly by a compression spring I 6 having one end received in a recess formed in the lower end of a block Il of conducting material which is bonded to the inner face of the cup-like member In and which, in effect, forms a continuation of the conducting stud I I. As illustrated in the drawing, the compression spring engages a cup-like enlargement I8, formed on the upper end of the sleeve I5, and surrounds a guide rod I9 which is secured in fixed. relation at one end to the block il and which is slidably received in an opening in the insulator I l to maintain the nlamentary cathode structure centrally positioned. The cathode structure includes two groups of parallel rodlike members I2 having the upper ends thereof connected with a pair of generally circular conducting members 20 and 2I which are supported in spaced and insulated relation from the members 8 and I'I. The member 20 is connected by an elongated conductor 22 to a conducting ring 23 bonded to the inner base portion of the U- shaped terminal 8. In a similar manner, the other group of cathode conductors l2 is connected with the body ll, and as a result with the stud Il, by an elongated conductor 2d. As illustrated, the conductor i213 is formed from iiat stock and provided with a half turn in the centr-al portion thereof. This construction equalizes the resilience of supporting conductor 2d and the longer support 22, with the result that damage to the filament by mechanical shock is substantially eliminated.

The control and screen grids are of similar construction and are mounted in a similar manner from the ring terminals provided by the members 5 and 'I of the envelope. The grids are each of the rod type; that is, they comprise a plurality of generally parallelrods arranged in a cylindrical array. In order to reinforce the structures, however, an open spiral is wound about the cylindrical structure and bonded to the individual grid conductors at each fcrossover point. As illustrated in the drawing, the control grid includes a plurality of rods arranged in a cylindrical array and secured at theirupper ends to a conicalsleeve 25 which is flanged at its upper end. The sleeve 25' is connected with the transverse portion of the steplike metal member 1 by an additional conical sleeve 26 which -is hanged at either end with the anges being bonded respectively with the flange of the sleeve V25 and the transverse portion of the member l. VIn a similar manner, the screen grid includes a plurality of elongated conductors 28 joined at their upper ends to a flanged conical sleeve 29 `and supported from the transverse portion of the member 5 by a second conical sleeve 30. The screen grid is provided with a con tinuous cup-like end cap 3l which provides more complete shielding between the control grid and anode circuits. The reinforcing helical wire 3,2 has been illustrated only on the control grid structure. It will' be understood that it may be employed on the screen grid structure as well.

From the foregoing detailed description, it will be apparent that terminals for the cathode heater supply are provided by the stud il and therannular terminal '8 which are concentrically arranged at one end of the device. VThe member 8 lalso yprovides a high frequency terminal for the cathode circuit, In asimilar manner, the wmembers 5 'i provide ring terminals of relatively large area for the screen and control grids,respectively. The anode being of cylindricalst-ructure and 'forming vpart 'of 'the envelope provides .a directly accessible connection for the anodecirc-uit'which maybe completed through 'a cylindrical radiatorY (not shown) surrounding the anode. This construction provides extensive contact area and as a result of the stepwise conguration of the envelope, the installation and removal of the discharge fromassociated circuit components is facilitated. The particular shape of the sealing members E and 7i, in addition to providing the stepwise vconiiguration ofthe envelope, provides means for `supporting'the controland screen grid'structures by means ofthe conical supports. .As a result, the electric discharge device is easilyassembled and .has desirable electrical characteristics for relatively high frequency operationin that the inductance of the internal connections with the variouselements of the tube is kept at a minimum and the internal shielding is very complete. By making the supporting structures for the screen and control grids in two parts, assembly of the discharge device is facilitated. For example, it is possible to assemble the upper portions 26 and 3i] oi the conical supports .in the envelope and to secure the grid assemblies including the lower portions 25' and 29 of the supports before making the iinal seal in the envelope structure which may, for example, be made between the parts 2 .and i3. lAs 'will be readily understood by those skilled in the art, it is difficult to obtain desirable high frequency operating characteristics in electric discharge devices of relatively high power rating. The features 0f the present invention contribute to a marked degree to a desirable combination of operating characteristics at high 'frequencies and-high power output.

While I have shown and described a particular-embodiment lof my invention, -it will be 'apparent -to those skilled in the-art that changes and modifications may be 'made without departing from .the features of my invention, and I, therefore, aim .in the appended claim to cover all such changes and modifications as fall within the true spirit `andvscope of Amy invention.

What Iclaim vas new and ldesire to secure by Letters .Patent of the United. v.States is:

en velectric discharge devicelcomprising an .en-

velope including va three hollow .cylindrical 1in.-`

sulators. of progressively -decreasing `diameter arranged .in axiallyspaced.relation, a-pair--of sealing` members each positioned .respectively :between :successive Viones of said -cylindrical vinsulators in .said lenvelope wall and `each vincluding cylindrical portionsY of different diameters-corresponding .respectively tothe diameters of the insulators .to whichthey .arejoined and an lintermediate .transverse portion, a hollow cylindrical anode supported from oneiend vof the VVlargestfof said insulators, -a vcathode extending into said anode .and including r,two terminals, .anannular metal `member .having the llarger edge thereof sealed to one `end of the smallest.ofsaid-cylindrical .insulators and fthe -smalleredge sealed in insulatedV .relation -to a terminal member received within. the opening of said annular member, the terminals of said :cathode being -connected respectively with said annular member and said terminal vmember and apair offcontrol electrodes includinggenerally cylindrical .metal-supports interposed between said anode and said cathode withsaid supports each `.ioined-.at--one Vend to the transverse .portion yci" one `of said -metal sealingmembers. Y

fHARRY TL. THOR'SQN.

REFERENCES CFB-,ED

The vfollowing references are offrecord in the file of this patent:

UNITED STATES PATENTS Number Name `Date 2,411,046 Liimatainen Nov. 12, 1946V 25,416,315 Hartman Feb. 25, 1947 2,419,578' Litton V Apr. 29, 1947' 72,423,319 Chevigny July 8, 1947 

